Optical member

Abstract

Disclosed is an optical member for use in liquid crystal displays, which can correct the light path and can minimize the loss of light, so that light in a wider angular range can be collected forwards. Even when a distance between the optical member and a light source is shortened, the optical member can exhibit good hiding performance and prevent deformation caused by heat. Upon expansion and shrinkage, the optical member is not scratched and does not generate noise at a portion in contact with a support pin.

The invention claimed is: 
     
       1. An optical member, comprising a substrate layer and a structural layer formed on one surface or both surfaces of the substrate layer and having an array of a plurality of repeated, curved three-dimensional structures,
 wherein each of the curved three-dimensional structures of the structural layer has a height that is a peak of the curved three-dimensional structure and a distance that is a pitch of the repeated three-dimensional structures, and each of the curved three-dimensional structure is comprised of, when viewed in longitudinal cross-section, a center first zone having a predetermined curvature k in both directions from a peak thereof, as represented by Equation 1 below in an x-axis and y-axis coordinate system in which the peak is set to an origin of the system, and two second zones abutting on both sides of the first zone and having an inclination angle relative to the substrate layer: 
 
       
         
           
             
               
                 
                   
                     k 
                     = 
                     
                       
                         
                           - 
                           2 
                         
                         ⁢ 
                         y 
                       
                       
                         x 
                         2 
                       
                     
                   
                 
                 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                 
               
             
           
         
         (wherein x is a real number other than 0, and y and k are real numbers); 
         the first zone has a curvature k of 0.05-0.30; 
         each of the second zones has an inclination angle of 30-50° or 130-150° relative to the substrate layer; 
         the pitch of each of the three-dimensional structures, which is defined as the distance of the individual three-dimensional structure in contact with the substrate layer and is a sum of the distance of the first zone in contact with the substrate layer and the distances of the second zones in contact with the substrate layer, is 100-500 μm and the height of each of the three-dimensional structures is 25-300 μm; and 
         the distance of the first zone in contact with the substrate layer is ⅓-⅗ of the pitch. 
       
     
     
       2. The optical member according to  claim 1 , wherein each of the three-dimensional structures of the structural layer has a longitudinal cross-section which is symmetrical with respect to a vertical centerline passing through a peak point thereof. 
     
     
       3. The optical member according to  claim 1 , wherein the substrate layer has irregularities and a surface roughness Ra of 2˜40 μm. 
     
     
       4. The optical member according to  claim 1 , wherein, when the structural layer is formed on one surface of the substrate layer, the optical member further comprises one or more selected from the group consisting of:
 a bottom layer formed on a surface of the substrate layer opposite the surface having the structural layer; and 
 a top layer formed on a surface of the structural layer opposite the surface having the substrate layer. 
 
     
     
       5. The optical member according to  claim 4 , wherein the one or more selected from the bottom layer and the top layer have irregularities and a surface roughness Ra of 2˜40 μm. 
     
     
       6. The optical member according to  claim 4 , wherein the one or more selected from the bottom layer and the top layer have a thickness of 10˜300 μm. 
     
     
       7. The optical member according to  claim 4 , wherein the one or more selected from the bottom layer and the top layer include particles which are used in an amount of 0.01˜40 parts by weight based on 100 parts by weight of a resin for the bottom layer or the top layer. 
     
     
       8. The optical member according to  claim 1 , further comprising a slip layer formed on one or more surfaces selected from the group consisting of an uppermost surface of the optical member and a lowermost surface of the optical member, and having a surface friction coefficient of 0.25 or less and a thickness of 1˜300 μm. 
     
     
       9. The optical member according to  claim 8 , wherein the optical member has a hole having a depth of 15 μm or less after a vibration test, in which the depth of the hole is measured by mounting the optical member to a backlight unit for a liquid crystal display panel, fixing the optical member to a vibration tester, performing the vibration test under conditions of 10 min at 10 Hz and 20 min at 60 Hz thus forming the hole in a lower surface of the optical member at a position which is identical to that of a support pin located at a center of the backlight unit, measuring a height deviation Z between a highest portion of the hole and a lowest portion of the hole using a laser scanning microscope, performing the measurement three times at the above position, and determining an average value of three measurements. 
     
     
       10. The optical member according to  claim 8 , wherein the substrate layer, the structural layer and the slip layer are formed by co-extruding a base resin for the substrate layer and the structural layer and a resin for the slip layer while passing through a pattern roller. 
     
     
       11. The optical member according to  claim 10 , wherein the base resin is selected from among a resin mixture of polycarbonate and polystyrene mixed at a weight ratio of 1:9-9:1, a polycarbonate resin, a polystyrene resin, a methylmethacrylate resin, a styrene-acrylic copolymer resin, and an olefin resin. 
     
     
       12. The optical member according to  claim 8 , wherein a resin for the slip layer is selected from among a fluorine resin, a styrene-butadiene copolymer, wax and rubber. 
     
     
       13. The optical member according to  claim 8 , wherein a resin for the slip layer is a styrene-butadiene copolymer and comprises one or more selected from among fluorine resin particles, styrene-butadiene copolymer particles, wax particles and rubber particles. 
     
     
       14. The optical member according to  claim 1 , wherein the substrate layer and the structural layer are formed by co-extruding a base resin for the substrate layer and the structural layer while passing through a pattern roller. 
     
     
       15. The optical member according to  claim 14 , wherein the base resin is selected from among a resin mixture of polycarbonate and polystyrene mixed at a weight ratio of 1:9-9:1, a polycarbonate resin, a polystyrene resin, a methylmethacrylate resin, a styrene-acrylic copolymer resin, and an olefin resin. 
     
     
       16. The optical member according to  claim 1 , wherein the substrate layer is formed of any material selected from among a polyethyleneterephthalate resin, a polymethylmethacrylate resin, a polycarbonate resin, a polypropylene resin, a polyethylene resin, a polystyrene resin and a styrene-acrylic copolymer resin, and
 the structural layer is formed of any material selected from among a polymer resin group including a UV curable resin and a thermosetting resin. 
 
     
     
       17. The optical member according to  claim 1 , wherein the optical member is subjected to antistatic treatment. 
     
     
       18. The optical member according to  claim 1 , wherein the optical member has a total light transmittance of 90% or more and a haze of 90% or more. 
     
     
       19. The optical member according to  claim 1 , wherein the optical member has a Weber fraction of 1.0 or less, as represented by Equation 2 below: 
       
         
           
             
               
                 
                   
                     
                       Weber 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       Fraction 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         ( 
                         % 
                         ) 
                       
                     
                     = 
                     
                       
                         
                           
                             Lumi 
                             · 
                             
                               ( 
                               max 
                               ) 
                             
                           
                           - 
                           
                             Lumi 
                             · 
                             
                               ( 
                               min 
                               ) 
                             
                           
                         
                         
                           Lumi 
                           · 
                           
                             ( 
                             max 
                             ) 
                           
                         
                       
                       × 
                       100 
                     
                   
                 
                 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                 
               
             
           
         
         (wherein Lumi. is luminance). 
       
     
     
       20. A backlight unit assembly, comprising:
 the optical member of- claim 1 ; and 
 at least one selected from among a prism sheet and a light diffusion plate. 
 
     
     
       21. The backlight unit assembly according to  claim 20 , wherein the optical member is spaced apart from a light source by a distance of 2-10 mm.